Simmons started to work as costumer in the early 1980s on projects such as the comedy ...All the Marbles (1981), the television series Paper Dolls (1984, starring Richard Beymer, Terry Farrell, and Jonathan Frakes), the comedy Movers & Shakers (1985), the crime mystery Clue (1985, with Ken Harvey), the science fiction comedy Spaceballs (1985), and the television comedy Maybe Baby (1988).

Following her work on Star Trek, she worked as costume supervisor on the final season of the drama series Falcon Crest (1989-1990) and then became the costume supervisor/ costume designer on the comedy series Seinfeld (1992-1998, starring Jason Alexander). Other projects as costumer/ costume supervisor include the television musical Polly: Comin' Home! (1990), the action film The Last Boy Scout (1991), the crime drama Blow (2001, with Cha Blevins and Anthony J. Scarano), the animated adventure Looney Tunes: Back in Action (2003), and the action sequel xXx: State of the Union (2005).

As costume designer, Simmons worked on the action comedy For Better Or Worse (1995, starring Jason Alexander), the comedy series The Single Guy (1995-1997), the crime drama Red Letters (2000), and the television series Bob Patterson (2001) and My Big Fat Greek Life (2003). Between 2006 and 2011 she worked as costume designer on the daily show The Tonight Show with Jay Leno.